The long range purpose of this project is to study the cell surface, how it may change in transformation to malignancy, either spontaneously, or as induced by SV40 virus. Topics of present interest are 1) Changes in protein and glycoprotein components, and correlation with cell growth properties in tissue culture and in vivo in the syngeneic and in the nude mice; 2) Controls of expression and methods of purification of surface antigens and tumor specific transplantation antigens; 3) Selection of phenotypic and genotypic revertant cells which lose SV40.